The present invention relates to the manufacturing process for a direct positive silver halide photographic emulsion. It particularly relates to the manufacturing process for an ultra-low sensitive direct positive silver halide photographic emulsion used for a photosensitive material capable of being used in a daylight room that is used in photoengraving for printing. Recently, a higher efficiency in a contact printing process has been requested in the printing field due to the complicated nature of prints or to the advancement of scanners. For this request, the improvements both in equipments such as printers and in photosensitive materials have been made and in the field of photosensitive materials, there has been developed an ultra-low sensitive (it is 10.sup.-4 .about.10.sup.-5 times conventional contact printing film in sensitivity) silver halide photosensitive material called a daylight room photosensitive material and capable of being used in a daylight room illuminated by an ultraviolet intercepting fluorescent lamp, an incandescent electric lamp or by a yellow fluorescent lamp.
For the further improvement for higher quality, it is necessary to study and improve the composition, the shape and grain distribution etc. of silver halide grains for photographic emulsions. An example of the means therefor includes the pH conditions in preparation, the control of pAg conditions or the like and the improvement in the mixing method.
However, aforesaid well-known preparation method for silver halide grains do not, even after being applied to the preparation of photographic emulsions for direct positive daylight room photosensitive materials capable of being used for the duplex, result in a satisfactory level on the points of gamma of photographic characteristics curve Dmin and halftone quality etc.